2001-2010年鄱阳湖采砂规模及其水文泥沙效应

Hydrological and sediment effects from sand mining in Poyang Lake during 2001-2010

在长江主河道采砂行为于2000年全面禁止之后,受中国长江中下游房产建筑行业的砂石需求的驱动,大量采砂船转移到鄱阳湖采砂,这种规模化的采砂行为对鄱阳湖的水文环境产生的影响还缺乏定量研究。本研究通过利用地形数据、水文数据和卫星遥感数据,分析了鄱阳湖2001-2010年的采砂场的空间分布和采砂量,定量分析了采砂行为对鄱阳湖水文和泥沙的影响。研究结果表明:1 2001-2007年鄱阳湖采砂船主要集中于松门山以北的通江河道,2007年以后采砂行为扩张到鄱阳湖中部;2 2001-2010年间,鄱阳湖采砂面积范围大约为260.4 km2,挖沙平均深度4.95 m,采砂量达到1.29×109m3或2154 Mt,体积上相当于使鄱阳湖库容增加了6.5%,重量上相当于1955-2010年以来鄱阳湖自然沉积量的6.5倍;3鄱阳湖采砂通过扩大通江河道的过水断面面积,加快了湖水注入长江速率,是引起近年来鄱阳湖秋冬季枯水期提前、枯水期延长的主要原因之一;4鄱阳湖采砂过程中通过挖沙、洗沙使沙场附近的水体含沙量增加、水体透明度降低,从而影响长江河道的泥沙平衡。

Sand mining has been practiced in rivers, lakes, harbors and coastal areas in recent years in China mostly because of the increasing demand for building materials in construction industry. Sand mining in Poyang Lake has been intensified since 2001 because such practice was banned in the Yangtze River and profitable. Meanwhile, the decline of water level of the Poyang Lake has aroused much more attention from researchers. The decline has been ascribed to a decrease in precipitation in Poyang Lake watershed, attenuation of congestion effect because of the Three Gorges Project and sand mining in the Poyang Lake. In this study, we analyzed the magnitude of sand mining in Poyang Lake using Digital Elevation Model（DEM） data from two periods and sand vessels distribution detected by remote sensing images. Another two Landsat images were used to evaluate the morphologic change compared with natural sedimentation, inundation extent and shoreline shape. And a hydrological dataset including water level, water discharge rate and sediment content for a long time series were used to analyze the hydrological effect and sediment effect from sand mining.Results showed that：（1） sand mining region was mainly distributed in northern Poyang Lake before 2007, but was extended into the central region and even to the channels of major tributary rivers into the Poyang Lake;（2） the area of sand mining was about 260.4 km^2. The magnitude of sand mining in Poyang Lake was about 2,154.3 Mt or 1.29 × 10^9m^3 during 2000-2010 with the assumption of sand bulk density of 1.67 t m- 3. It is almost 6.5 times of the natural sedimentation in volume during 1955- 2010;（3） sand mining affected the hydrologic regimes including increased areas of water discharge sections and water turbidity. Sand mining could be one of the most important factors that caused the decline of water level of Poyang Lake in drought season. It also affected the sediment pattern of the lower reaches of the Yangtze River.